[dataimport] Allow to replace escape char in the create_copyfrom_buffer

[doc] fix function name FTIRANK

[json] enable jsonexport selection on empty rsets (closes #2544358)

[test] fix req default value handling in CubicWebTC.view (closes #2544376) It's no more than the standard ``if rset`` vs. ``if rset is None`` error.

[ajax] fix attribute lookup (closes #2491038)

[server] add debugging for Hooks & Operations (closes #2470048)

[dataimport] Add SQL Store for faster import - works ONLY with Postgres for now, as it requires "copy from" command - closes #2410822 This store will use: - copy from for massive insertions. - execute from for update. The API of this store is similar to the other stores.

[test] swap order in assert of `test_users_and_groups_non_readable_by_guests` unittest2 order is (expected, got), not the opposite. This help test report readbility.

[test] fix server/querier/build_descr1 test. There is no self.transaction of TestCase. I assumed the test writer meant a session. This seems to make the test pass.

[server] make `test_bfss_fs_importing_transparency` less verbose on failure Dumping the whole content of a file on failure is a bit annoying. We only print the bad version here (it's usually the file path).